On warm sunny days, female hoverflies are often observed feeding from a wide range of wild and cultivated flowers. In doing so, hoverflies serve a vital role as alternative pollinators, and are suggested to be the most important pollinators after bees and bumblebees. Unless the flower hoverflies are feeding from is large, they do not readily share the space with other insects, but instead opt to leave if another insect approaches. We used high-speed videography followed by 3D reconstruction of flight trajectories to quantify how female Eristalis hoverflies respond to approaching bees, wasps and two different hoverfly species. We found that, in 94% of the interactions, the occupant female left the flower when approached by another insect. We found that compared with spontaneous take-offs, the occupant hoverfly’s escape response was performed at ∼3 times higher speed (spontaneous take-off at 0.2±0.05 m s−1 compared with 0.55±0.08 m s−1 when approached by another Eristalis). The hoverflies tended to take off upward and forward, while taking the incomer’s approach angle into account. Intriguingly, we found that, when approached by wasps, the occupant Eristalis took off at a higher speed and when the wasp was further away. This suggests that feeding hoverflies may be able to distinguish these predators, demanding impressive visual capabilities. Our results, including quantification of the visual information available before occupant take-off, provide important insight into how freely behaving hoverflies perform escape responses from competitors and predators (e.g. wasps) in the wild.
Bibliographical noteFunding Information:
This work was funded by the Air Force Office of Scientific Research (FA9550-15-1-0188 to P.T.G.-B. and K.N.), the Biotechnology and Biological Sciences Research Council (BB/L024667/1 David Phillips Fellowship to T.J.W.), Australian Research Council (DP170100008 to K.N.), Stiftelsen Olle Engkvist Byggmästare (2016/348 to K.N.) and Stiftelsen Längmanska Kulturfonden (BA17-0812 to K.N.). Deposited in PMC for immediate release.
© 2018. Published by The Company of Biologists Ltd
- Foraging behavior
- Looming stimuli
- Motion vision
- Retinal size
- Target detection